Ignition system



F- J. HoovEN IGNITION SYSTEM Filed March 9, 1938 QOOQ L ft/40, 1%

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f INVENTOR Jawa/./p/vm ATTORNEY.

, Y Patented-Nat. 21,1939

UNITED-f STATES PATENT OFFICE IGNITION SYSTEM Frederick J. Hooven,Dayton, Ohio Application March 9, 1938, Serial No. 194,784

12 Claims.

This invention relates to ignition systems such as are used on internalcombustion engines.

One object of the invention is the provision of ignition means whichenables the use of a coil small enough to be built integral with thespark plug of an engine or the like, allowing the elimination of radiointerference without the use of extended shielded high voltage leads,and especially adapted for high speed engine operation.

Another object of the invention is the provision of ignition means inwhich the energy of the spark is substantially the same regardless ofthe speed of engine operation, making it possible to regulate the sparkenergy to a value which will 15 give eillcient operation at all speedswithout requiring the provision of an excessive energy at any particularspeed, and reducing the deterioration of spark plug electrodes andcontact points.

Another object of the invention is the provision of an ignition systemfor producing successive sparks and including a condenser or condenserswhich are charged from a source of charging current periodicallyconnected thereto and which are discharged periodically through atransformer Winding or windings which are also effective in providingpart of the charging circuit for the condenser.

Another object of the invention is the provision of an ignition systemin which a pair of condensers are alternately charged from a commonsource of charging current and periodically discharged alternatelythrough diierent primary windings of spark coils to thereby energizelsaid primary windings.

Another object of the invention is the provision of an ignition systemhaving a continuous source of charging current connected uninterruptedlyto a storage condenser and connected to a coil energizing condenser orcondensers by means of a single series of distributor contacts whichestablish circuits for the charge or discharge of the coil energizingcondenser or condensers through the coil windings, the constructionbeing such that the distributor contacts open at a time when no currentis flowing through them. Another object of the invention` is theprovision of an ignition system having a distributor in a. low voltagecircuit which periodically establishes connections between condensersand the primary windings of spark coils which are arranged at the sparkplug locations where they are effectively shielded against electricalradiation, the distributor also controlling the charging of thecondensers.

(Cl. 12S- 148) Another object resides in the method oi opera-` tion ofan ignition system of the character referredvto. 1

Other objects and advantages of the invention will be apparent from thefollowing description, the appended claims, and the accompanying drawingin which:

Fig. 1 is a diagrammatic showing of the various electrical connectionsof an ignition system embodying the present invention;

Fig. 2 is a diagrammatic showing of a modled construction in whichrectifying space discharge tubes are provided in the circuits connectedto the distributor; and

Fig. 3 is a vertical sectional view of a spark plug and coil unit.

Referring more particularly to the drawing by reference numerals, Fig. 1shows an electrical ignition system for producing electric sparks at anumber of spark gaps, the system being especially adapted for energizingthe spark plugs of an internal combustion engine and particularlyengines adapted for aeronautical use. 4In Fig. l the several spark plugsof the engine are designated l0, Il, l2 and i3, it being understood thatthese plugs may be of any suitable number in accordance with the numberengine.

In the usual ignition system of airplane engines, the distributor isprovided in the high voltage part of the system and the high voltageWires leading from the distributor to theseveral spark plugs of theengines are shielded to prevent radio interference by metal casingswhich increase the capacity effect of the high voltage part of thesystem to such an extent as to require the supply of comparatively largeamounts o1 power in the production of the sparks at the spark plugs. Inaccordance with the preferred arrangement of the present invention,however, the distributor is provided in the lower voltage part of thesystem and the primary windings of the spark coils are arranged closelyadjacent the spark plugs themselves so that the wires leading to theprimary windings at the spark plugs are comparatively low voltage wiresand their shielding may be effected where they extend from thedistributor to the spark plug locations without substantially increasingthe capacity effect of the high tension part of the system. Thus thecentral electrode I5 of the spark plug Il! is connected to one end ofthe secondary winding l 6 associated with that spark plug, the other endof the secondary I6 being connected to the metal body portion I8 of thespark plug as shown diaof cylinders in the l coils. The four transformercoils are designated 23, 24, 26 and 23 and include the primary windings21, 28, 29 and 30 respectively.

'I'he several primary windings of the transformer coils 23 to 28inclusive are electrically connected' to a common-lead 32 which ispreferably grounded and to the several leads 23,', 24', 25', and 26which extend respectively to contact members 23a, 24a, 25a, and 26a of adistributor. Cooperating with these contact members are additionalcontact members 23h, 24h, 25h and 26h respectively, the contact membersto which the same numbers are applied cooperating with one another andbeing normally open or disconnected, but being periodically connectedtogether to establish an electric circuit by means of a cam 34 providedon the rotatable distributor member 3E. It will be understood that thedistributor member 35 is carried by a rotatable shaft 36 which isoperated in timed relation with respect to the several engine cylindersso as to close the several circuits periodically and successively toproduce sparks at the spark plugs at the required time.

'I'he engine with which the spark plugs vare associated is provided withan electrical generator 31 which may be driven from a separatebattery-operated motor 39 or which may be connected mechanically to theengine shaft as desired. This generator, which is preferably adapted tosupply direct current of a voltage preferably of the order of 250 volts,is connected across a condenser 38 which may have a capacity of about 4microfarads and which acts as an electrical storage or reservoir member.Connected across the storage condenser 38 there are two coil energizingcondensers 40 and 4|, one side of each of these condensers beingconnected to opposite sides of the storage condenser 38 to which anuninterrupted supply of direct current is furnished from the generator31. The two condensers 40 and 4|, each of which may have a capacity ofabout .3 microfarad, are connected to the common wire 32 which leads tothe several primary windings of the transformers. The wires 42 and 43which extend from those sides of the condensers 40 and 4| that areconnected to the source of charging current extend to alternate contactmembers of the distributor as shown, the Wire 4 2 being connected to thecontact members 24b and 2Gb while the wire 43 is connected to thecontact members 23h and 25h. These wires 42 and 43 are preferablyenclosed in metal shielding tubes 44 and 46, and shielding tubes 41 areprovided to enclose the wires 23', 24', 25' and 26' and 32 throughouttheir extent to the transformer windings at the spark plug locations.

The operation of the described arrangement is v such that the condensersMl and 4| are periodically and successively connected to theuninterrupted source of charging current furnished from a suitable D. C.supply source such as generator 31 and storage condenser 38, and arecharged thereby; and are periodically connected to the transformer coils'and discharged or charged through the transformer coils which are thusenergized to produce a suiiiciently high voltage across the ends of thesecondary windings to cause sparking at the spark plugs. With the twocondensers 40 and 4| connected as shown through the distributorcontacts, one of these condensers will be discharged through a primarywinding of through Wire 32 to the point 48. This places the primarywinding 21 across the condenser 4| so that the'charge on that condenseris dissipated through the winding 21 and a spark is thus producedbetween the electrodes I5 and Il of the spark plug I0. And since theprimary winding 21 is placed across the condenser 4| that winding 21will form a conductive path through which the condenser 40 will becharged from the storage condenser 33. The charging current of condenser43 and the discharging current from condenser 4| act together, oneadding to the effect of the gther to produce a current ow through thewind- As the distributor cam 34 continues to rotate in a clockwisedirection it will open the circuit to the winding 21, and since the twocondensers 4i and 4| are connected in series across the chargingcondenser 38, the charge of the condenser 4l will be maintained and thecondenser 4I will remain in a discharged state until the contacts 24aand 24h are connected together by cam 34. 'I'he closing of thesecontacts connects the primary winding 28 of transformer coil 24 to Athewire 42 and the return wire 32, thus placing the winding 23 across thecondenser 40, and therefore placing it in series with the condenser 4|across the charging source 31, 33 so that the condenser 4B will now bedischarged through the winding 23, and the condenser 4| will be chargedfrom the charging source through the winding 28. The distributor thenopens the circuit to the winding 23 and closes the circuit to thewinding 29 as the distributor cam continues its rotational movements,thewlnding 23 thus being connected across the condenser 4|, whichdischarges again, and connected in series with the condenser 40 whichcharges again. These operations are repeated in timed succession so thateach condenser is periodically charged and discharged at successivesparking times, iirst one of the condensers and then one of the othersbeing connected through a primary winding to the storage generator 31and condenser 33 which are suiciently large in capacity, as comparedwith the size of the condensers 40 and 4I, to supply a charge to thosecondensers between the time elapsing from the opening of a pair ofcontacts of the distributor to the closure of the next succeedlng pair.The storage or reservoir condenser 33 is itself maintained substantiallycharged as it is connected continuously to the generator 31. Thegenerator itself may be of comparatively small size.

Even though the two condensers 40 and .4| are not the same in capacityeifect, the charging current of one added to the discharging current o fthe other is substantially constant, so that the several primarywindings associated with the several spark plugs are supplied with thesame amounts of current, and sparks of substantially uniform intensityare successively produced at the several s park plugs. Even if one ofthe condensers 40 and 4| is entirely omitted, if the capacity of theremaining condenser is sumcient, it will supply sumcient current irst bycharging through and then lay-discharging across the successive' primarywindings.

To provide a hotter spark under starting conditions or for emergency, apair of auxiliary condensers 49 and 50 are connected in series acrosstions, however, the switch 5i is open, and the condensers 49 and 50remain connected across the reservoir condenser 38 and thus theythemselves act as reservoir condensers and serve to increase thecapacity of the storage or reservoir part of the system. Under normalconditions of operation, after the engine has been started, a hot sparkis not required, and a spark that is hotter than necessary is even adisadvantage as it increases the wear or deterioration of the spark plugelectrodes.

It will be understood that the time required for the discharge of acondenser 40 or 4I and the .charging of the other one of thesecondensers through a primary winding is exceedingly small, so that a owof current takes place across the contacts 23a and 23h for example asthose contacts approach one another and even a little before they close,it having been found that the time during which current ilows acrosscontacts 23a and 23h is so exceedingly small that the ow probably ceasesbefore the contacts actually touch one another. When these contacts 23aand 23h open, the iiow of current through the winding which they connectin circuit has stopped so that no ow of current is interrupted as thesecontacts separate. This entirely eliminates sparking across the contactsof the distributor at the time of opening ofthe contacts, and any sparkproduced as the contacts close does not adversely affect the operationbecause the Voltage is suiliciently high when the contact is made toinsure instantaneous ow of current even if the contacts are pitted. The

contacts may therefore remain in service for very extended periods oftime even though they are made of ordinary cheap material, for exampletungsten.

It will also be apparent that in the form of construction described, asingle series of distributor contacts are provided in the low voltagepart of the system which requires no supplemental circuit breaking orinterrupting devices, since the opposite sides of the condensers.

\ 40 and 4l, arranged in series,v are connected continuously across anuninterrupted supply of charging current. The arrangement is such thatno interval of time is required, as is customarily necessary betweensparking impulses, for the recharge of an energy reservoir, such asbuilding up a current in a coil or the' recharging of a condenserpreparatory to the production of a succeeding spark. This greatlyreduces the minimum time between successive sparks and allows the sparksto loe-created as often as desired, thus removing the limitations on thespeed of operation even in an engine having many cylinders.

In accordance with the present invention the natural frequency ofoscillation of the ignition system is extremely high. The higher thenatural eiect of oscillation of the system, the less it is affected byleakage resistance across the fected by a leakage resistance of 25,000ohms Yacross the gap, whereas a high grade magneto .of conventionalconstruction is unable to perform satisfactorily with a leakageresistance less than about 200,000 ohms. This factor is very importantbecause, in addition to serving as an increased safety factor, it allowsthe use of a much colder running spark plug. With a cold running sparkplug, an important obstacle to the development of high output engines isremoved, for as is well known, the limitation in the increased coolingof spark plugs is thetendency for them to foul up with deposits ofcarbon or other material while idling or running at part load, and withvconventional ignition systemsit is necessary to operate the plug sothat it becomes hot enough to burn oi such carbon deposits in order toprevent electrical leakage such as would cause misring.

In accordance with the modiiied arrangement shown in Fig. 2, there is asimilar arrangement of a motor 39 operating a generator 31 which isconnected to a storage 'condenser 38. to auxiliary starting condensers49 and 50' and to the coil energizing condensers 40 and 4l'. The sparkcoils including the primary windings 21, 28', 29'nand 30' are similarlyassociated with the secondary windings and with the spark plugelectrodes and are similarly connected to the contact members of thedistributor 35. However in this construction rectifying space dischargetubes 53 and 54 are connected to the wires 42 and 43 between thecondensers 40' and 4|'v and the contact members 51, 59 and 58, 60 ofthedistributor. The space discharge tube 54 comprises spaced elements 6land 62 and an energizing or grid element 63, the latter being connectedto impedances 64 and' 55 and a small condenser 66 as shown so that whenthe contact 51 closes current ows through the winding 21', `through theimpedance 64 to the l grid 63 and then through the gas contained withinthe tube to the element 6l, this flow of current between the elements 63and 5l rendering the gas which separates elements 6l and 62 conductiveso that the flow of 'current then takes place 'across those elements.The impedance of part 64 may be suflcient to slightly delay the time atwhich the main current iiow starts across elements 5I and 62 .so thatthe contact 54 will be closed before this current llow starts. The,sparking effect across the contacts at the time the contacts close isthus eliminated. And as the glow tube provides for flow of current inone Adirection only between the electrodes 6l and 62, any surging oroscillation tendency that might otherwise be produced is completelydamped out instantaneously. The glow tubel 53 is similarly connected tothe wire 42'. The glow tubes are also effective in enabling a greatercharge to be appliedto the condensers than would otherwise be obtained.This may take place because the inductance of the primary winding of thespark coil and the capacity of the condenser 40 or 4l when connected tothat winding and charging can produce a voltage across the condenser inexcess of the voltage across the storage condenser due to theoscillatory currents that arise in the circuit and the inductive actionwhich builds up the voltage through the unidirectional path pro- Fig. 3shows the mechanical arrangement of the primary and secondary windingsVof a spark voltage coil or transformer on the spark plug itself. The

central electrode I5 is separated from the metal body I8 by suitableinsulation 10, the lower ends of the body I8 having fingers 1| providinga plu-f' rality of spark,gaps 12 to the central electrode. Detachablysecured to the body I8 of the spark plug is a metal casing shield 13, ofcylindrical form; having its lower end 14 threaded so it may be readilyengaged in a detachable manner with threads provided on the body memberI8. With.- in the casing 13A is a metal contact member 15 which may forma magnetic core for the secondary winding I6 which is preferablyarranged in honeycomb formation and which is electrically connecteddirectly to the contact member 15 at oneend of the secondary Winding.The other end of the secondary winding is electrically connected by wire16 to the metal casing and therefore to thebody member of the plug. Thewire 16 is also connected to one end of the primary winding 12, theother end of the primary winding being connected as indicatedat 11 to ametal contact member 18 which is provided above the insulation washer19. The wire 23', having a shielding conduit 41, extends through thecoupling member 80 and into the space 8l at the top of the casing whereit may rest on the contact member 18, being held down against thatcontact member by a spring 82 engaged by an adjustable holding screw 83which is threaded ln 'the top of the casing. An insulating disk 80a isprovided on the lug 84 at the end of wire '23' and between that lug andthe spring. When the screw 83 is loosened and removed, the lug 811 maybe liftd from the contact member 18 and pulled out through the openingwhich the coupling member provides.

The windings 21 and I6 are preferably surrounded and enclosed in ahomogenous body 86 of heat-resistant insulating material such as asuitable ceramic or plastic. The electrical connection between thesecondary winding of the coil and the central electrode of the sparkplug is effected by a spring blade 81 connected to the top of the plugelectrode and bearingyieldingly against the contact member 15, againstwhich it is held by means ofthe spring 82 which holds the entire coilstructure downwardly in a yielding manner'in the casing 13. The primaryand' secondary windings together with their enclosing shield whichprevents radio disturbance may thus be readily removed from the sparkplug itself and may be readily attached to the lead wire. The plug maybe connected to the engine by using a wrench on the usual hexagonal nutportion 89,

and the coil and casing then added, after which the wire 23 isconnected.

The primary winding 21 of the coil may consist cf about 25 turns appliedto a honeycomb secondary winding having about 800 turns, the latterbeing capable of generating current at sufciently high voltage of theorder of several thousand volts to break down the gap across the plugterminals. There are no long shielding wires to Vgreatly increase thecapacity of the high voltage part of the system, and the shielding of-the comparatively low voltage wires of the system is a simple matterand can` be accomplished without materially increasing the powerrequired by the high voltage system. Condensers may therefore be used toenergize the primary windings of the transformers and. to produce asuiiiciently hot spark for effective operation. And since the time'required for charging and discharging the condensers is almostinfinitesimal, the system' is especially useful for high speedaeronautical engines and especially enginesin which the eliminationofradio interference is 'a very desirable factor. y

While the methodand forms of apparatus herein described constitutepreferred embodiments of the invention, it is to be understood that theinvention is not limited to this precise method and these forms ofapparatus, and that changes may be made therein without departing fromthe scope of the invention which is defined in the appended claims.

What is claimed is:

1. The method of successively energizing the primary windings of sparkcoils to create sparks at successive spark plugs comprising periodicallycharging a condenser through a primary winding from a source of chargingcurrent while discharging a secondcondenser through the same primarywinding to thereby energize said primary windmg, and then dischargingthe first condenser through a second Winding while charging the secondcondenser through the second winding to thereby energize the secondwinding.

2. An ignition system of the character de- .scribed comprising a directcurrent generator, a

storage condenser connected across said generator, a coil energizingcondenser connected electrically at one side to one side of said storage4 condenser, a series of primary windings, a sec ondary winding for eachprimary winding, a series of spark gaps connected to\s`aid secondarywindings, and a series of contact means for alternately placing the coilenergizing condenser across a primary winding and subsequentlyconnecting the coil energizing condenser to the storage condenserthrough another primary winding, and means for operating said contactmeans in timed succession.

3. An ignition system of the character desaid storage means, a series ofprimary windings, a secondary winding and a spark plug associated witheach primary winding, and a distributor for successively connecting theprimary Windings one'at a time across one of said Condensers and at thesame time in series with the other condenser across said storage means.

5. An ignition system of the character described comprising a powersource of uninterrupted charging current, a pair of condensers, a

' series of transformer coils, a spark plug associated with eachtransformer coil, the transformer coils for the respective spark plugsbeing located at the spark plug locations, a distributor having circuitclosing means for each translformer coil, and connections between saidsource,

condensers, coils and distributor for placing one of said condensersacross a transformer coil whiler connecting the other condenser to thepower source through the same transformer coil.

6. An ignition system of the character described comprising a powersource of continuous charging current, storage means connected acrosssaid source, a pair of condensers connected across said storage means, aseries of primary windings, a secondary winding and a spark plugassociated with each primary winding, a distributor for successivelyconnecting the primary windings one at a time across one of saidcondensers and at the same time in series with the other condenseracross said storage means, a supplemental condenser, and means operableto connect said supplemental condenser across one of said pair ofcondensers.

'7. An ignition system of the character described comprising a powersource of continuous charging current; a pair of condensers connected inseries across said storage means, a series of primary windings, asecondary winding and a spark plug associated with each primary winding,a distributor for successively connecting the primary windings one at atime across a condenser and in series with the other condenser acrosssaid power source, and a rectifying space discharge tube connectedbetween each of said condensers and said distributor.

8. The method of energizing a transformer means to create sparks at thespark plugs of an ignition system comprising periodically charging apair of condensers alternately from a common source of charging current,and periodically discharging the condensers alternately through thetransformer means so that the charging current of one condenser and thedischarging current of the other condenser ow simultaneously through thetransformer means to energize the same.

9. The method of energizing the primary part of a spark coil system tocreate sparks at the spark plugs comprising periodically charging awinding energizing condenser mainly from a storage condenser and to acomparatively small extent from a direct current generator and passingthe charging current through a primary winding of the system to energizethe same, and

then discharging the energizing condenser 10. The method of energizingthe primary partV of a spark plug system to create sparks at the sparkplugs comprising periodically charging a condenser through a primarywinding'of the system from a source of charging current whilesimultaneously discharging a second condenser through the same windingto thereby energize the winding, and then discharging the firstcondenser through a primary winding of the system while simultaneouslycharging the second condenser from the same source.

11. An ignition system of the character described comprising a directcurrent generator, a storage condenser connected across said generatorcontinuously, a coil-energizing condenser connected electrically to oneside of said storage condenser, transformer means, a series of sparkplugs energized by said transformer means, and contact means foralternately connecting said coil-energizing condenser across thetransformer means and connecting said condenser to said storagecondenser through said transformer means to discharge and charge theenergizing condenser alternately at successive spark intervals.

12. An ignition system of the character described comprising a directcurrent generator, a storage condenser connected across said generatorcontinuously, a pair of energizing condensers connected in series acrosssaid storage condenser, transformer means, spark plugs associated withsaid transformer means, and contact means for placing one of saidenergizing condensers across the transformer means while simultaneouslyconnecting the other energizing condenser to the storage condenserthrough the transformer means.

FREDERICK J. HOOVEN.

